SMAR LD303, Operation And Maintenance Instruction Manual, Page: 34 / 110

LD303 - Operation and Maintenance Instruction Manual
3.8
LD303 - Cyclic Configuration
The PROFIBUS-DP and PROFIBUS-PA protocols have mechanisms against communication
failures between the slave device and the network master. For example, during initialization, these
mechanisms are used to check these possible errors. After powering up the field device (slave), it
can cyclically exchange information with the class 1 master, if the parameterization for the slave is
correct. This information is obtained using the GSD files (supplied by the device manufacturer, it
contains their descriptions). Through the commands below, the master executes all initialization
process with the PROFIBUS-PA device:
x Get_Cfg: uploads the slave configuration on the master and checks network configuration;
x Set_Prm: writes to the slave parameters and executes the parameterization network;
x Set_Cfg: configures the slaves according to its outputs and inputs;
x Get_Cfg: another command, where the master checks the slave configuration.
All these services are based on the information obtained from slave GSD files. The GSD file from
LD303
shows details such as, hardware and software revision, device bus timing and information
about cyclic data exchange.
LD303
has two function blocks: one AI (Analog Input) and one TOT (Totalizer). It also has the empty
module for applications where not all function blocks are necessary. The following cyclic order of the
blocks should be respected: AI and TOT. Suppose, only the AI block is necessary, then configure
this way: AI, EMPTY_MODULE.
Most PROFIBUS configuration tools use two directories where the different manufacturers’ GSD’s
and BITMAPS files are stored. The GSD’s and BITMAPS for Smar devices can be obtained through
the website: (
https://www.smar.com ), on the ‘download’ link.
The following example shows the necessary steps to integrate the
LD303
on a Profibus system.
These steps are valid for the entire 303 line of Smar devices:
x Copy the
LD303
gsd file to the research directory of the PROFIBUS configuration tool, usually
called GSD;
x Copy the
LD303
bitmap file to the research directory of the PROFIBUS configuration tool usually
called BMP;
x After choosing the master, define the baud rate for the network. Do not forget that couplers may
work with the following baud rate: 45.45 kbits/s (Siemens model), 93.75 kbits/s (P+F model) and
12 Mbits/s (P+F, SK2 model). The IM157 device link (Siemens model) may work up to 12
Mbits/s;
x
Add the
LD303
and specify its physical bus address;
x Choose the cyclic configuration via parameterization using the gsd file that depends on the
application, as detailed previously. For every AI (Analog Input) block, the
LD303
provides the
process variable to the master in 5 bytes value, being the first four according to float point data
type and the fifth byte is the status that brings the measure quality of this information.
In the TOT (Totalizer) block, the user can choose the totalization value (Total) and the integration is
made considering the operation mode (Mode_Tot). It allows defining of how the totalization will be,
with the following options: only positive value of the flow, only negative values of the flow, or both. In
this block, the user can reset the totalization and configure the preset value through the Set_Tot
parameter. The reset option is very used in batch processes;
It allows activating the condition of watchdog, which the device goes to a fail safe condition, when a
loss of communication is detected with the master.